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Counting bits in hardware: Reverse engineering the silicon in the ARM1 processor

Posted on Wednesday, January 13th, 2016 in ARM, reversed by DP

chip-labeled-bit

Ken Shirriff writes:

How can you count bits in hardware? In this article, I reverse-engineer the circuit used by the ARM1 processor to count the number of set bits in a 16-bit field, showing how individual transistors form multiplexers, which are combined into adders, and finally form the bit counter. The ARM1 is the ancestor of the processor in most cell phones, so you may have a descendent of this circuit in your pocket.

More details at Ken Shirriff’s blog.

This entry was posted on Wednesday, January 13th, 2016 at 4:03 pm and is filed under ARM, reversed. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

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